Disappointing Stirling engine - help, anyone??

As an introduction to model engineering, I have recently spent some time
buliding a Stirling engine from a kit I bought from Greenweld.
I was quite pleased to be able to carry out all the necessay procedures and now
have a model that turns very freely by hand. I tried to get it running with a
meths burner but with no luck. After a few trials, I got it running with a
block of ice on the cooler and a micro blow torch on the heat tube. It ran
nicely for a few minutes until the silver solder melted and the (very hot) cap
popped off and burned a hole in my workbench. Don't laugh - I haven't done this
sort of thing before!! But it should run on a much lower temperature
differential.
Has anyone ever built one of these kits and got it running? I have checked and
re-checked the instructions and can't find what I have done wrong. If I
disconnect the power piston from the flywheel and turn the engine by hand, there
is only about 2mm movement of the piston. I would expect quite a lot more
movement (10mm??) as this should be driving the engine. Any suggestions on where
else to start looking???
Stewart
Mansfield, Notts
Reply to
Stewart (not my real address)
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I'm afraid these kits are a none starter with out some modification. The displacer cylinder needs to be much longer and made of stainless stell. Copper is the worst material to use--to much heat conduction
Thses kits are primarily designed for school use in Germany. I expect it will put a lot of kids off metal work if they spend time making something that doesn't work.
Bob
Reply to
bob
Stirling engines are inherently inefficient at converting heat energy into mechanical energy. It is difficult or impossible to get many of the small model varieties to run because friction and lack of effectiveness in the components militates against it at that scale. (Which is not to say it hasn't been done). Regards Peter
Reply to
Peter J Seymour
Are there any larger model kits that don't cost an arm and a leg? The kits I have found on Google all seem to be a large amount over my budget.
Stewart Mansfield, Notts
Reply to
Stewart (not my real address)
'Fraid can't help you on that. My only experience is with some small American engines passed on from a relative. None would work as sold. One, however, was spectacular if a blowlamp was used as a heat source. Interestingly, the blowlamp flame converted the tarnished outer wall into shiny metal. Something to do with flame chemistry. However, I digress. Regards Peter
Reply to
Peter J Seymour
Excuse me?
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Stirling engines normally hold the "co-prize" for most efficient in the world, besides really big diesels.
A Stirling engine is the only engine design remotely efficient enough to run off coffee cups, candles, heat of your hand.
Of course, since there's so little energy (input) available, factors that don't matter in small comparitively high-power engines (e.g. steam engines) become inportant (such as friction).
If you're prepared to give a model stirling engine as much energy as other models, they run easily, but that defeats half the fun :-)
BugBear
Reply to
bugbear
Sorry to hear about your experiance Stewart - stirling engines can be really good fun!
I can vouch for the LK1 kit from the engineers emporium
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which I have had running off the heat of a hand. But it is significantly more expensive than the greenweld kit.
Another which should be OK (though I have no personal experience of it) is the PM research 'solar 1' (or kit form 'solar 13) available in the uk through bullnet
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I say should be ok as the design has been around for yonks having been originated by Davies Charlton in the 1950's.
The power available from these small stirling/hot air engines is tiny and they need to be very carefully assembled and checked for the slightest hint of binding or leakage if they are to be successful.
Reply to
Nick H
I can remember that one from school chemistry. A flame has three zones. A flame has an inner zone of unburned gas, a middle zone called the reduction zone and an outer zone called the oxidizing zone. The supply of oxygen to the redution zone is deficient and so the flame can remove an oxide layer (tarnish) placed in it.
I have found that my Stirling engine will actually run for a few seconds with a blowlamp on the heater tube, but as I have found out twice now, the temperature that it takes to run the engine is perilously close to the melting point of the silver solder holding the end cap in place. Also, it stops running even with a blowtorch when the cooler gets too hot, as expected.
Stewart Mansfield, Notts
Reply to
Stewart (not my real address)

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